Low volatile phosphorous gelling agent

ABSTRACT

Liquid hydrocarbons are gelled by the introduction of a phosphate ester and a crosslinking agent for use in oil recovery. Generally a proppant, delayed gel breaker and other modifiers are added to the gelled hydrocarbon to improve the oil recovery process. The phosphate ester used in this method and composition for oil recovery has low volatility and good stability during hydrocarbon distillation resulting in improved distillation efficiency in a refinery.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to gelled liquid hydrocarbon fluids and methodsof their use and preparation.

2. Description of the Prior Art

In order to maximize the amount of oil derived from an oil well aprocess known as hydraulic pressure stimulation or, more commonly,subterranean formation fracturing is often employed. Generally, a fluidis pumped under high pressure down the wellbore through a steel pipehaving small perforations in order to create or perpetuate cracks in theadjacent rock. The fluid employed must be able withstand exceptionallyhigh shear forces. Gelled liquids, particularly gelled hydrocarbons, areoften employed. In gelling the hydrocarbon on-site it is also preferredthat gellation occur as quickly as possible. In addition, delayed gelbreakers are used to cause the fracturing fluid to revert back to a thinfluid.

High viscosity gelled hydrocarbon containing a proppant material such assand is used in this stimulation process. Polyvalent metal salts ofphosphoric acid esters have been used to gel the hydrocarbon materialsfor this process. References include U.S. Pat. No. 4,622,155 issued toHarris and U.S. Pat. No. 5,846,915 issued to Smith on this process.Polyvalent metal ions include ferric or aluminum ion in thesereferences.

Rapid gellation of hydrocarbon liquids is also required when tanks orvessels containing such liquids are damaged during transit to avoid orreduce spillage and the resultant damage to the environment. A varietyof other applications exist which require the rapid gellation ofhydrocarbon liquids. Therefore, several means for gelling hydrocarbonliquids are disclosed in the prior art.

U.S. Pat. No. 5,417,287 to Smith et al. is directed to a method forfracturing a subterranean formation which involves adding to ahydrocarbon liquid (a) an organic phosphate of the formula HPO₄ RR′where R is an alkyl or alkaryl group having from 6 to 18 carbon atomsand R′ is hydrogen or an aryl, alkaryl, or alkyl group having from 1 to18 carbon atoms; and (b) a ferric salt.

European Patent Application No. 551021A1 to McCabe et al. is directed togelling a hydrocarbon liquid by adding thereto an at least partiallyneutralized alkyl orthophosphate acid ester, a C₈-C₁₈ surface activeamine and a C₂-C₄ monohydric alcohol. The surface active amine employedincludes alkyl and alkanol amines having from about 8-18 carbon atoms,N-heterocyclic amines, alkyl substituted derivatives of suchheterocyclics and mixtures thereof. Amines having more than one nitrogengroup are preferred and imidazoline such as that prepared from thereaction of a tall oil fatty acid with diethylenetriamine is mostpreferred.

U.S. Pat. No. 4,316,810 to Burnham is directed to a fracturingcomposition which is an aluminum salt of an oxaalkyl phosphate in an oilbase liquid. Surface active agents are not disclosed.

U.S. Pat. No. 4,153,649 to Griffin is directed to the reaction productof a hydroxy ether and a pentavalent phosphorus compound and an alcohol.The hydroxy ether has the formula ROR₁ OH wherein R is a C₁ to C₆ alkylgroup, R₁ is a C₂ or C₃ alkylene group and the total carbon atoms of R₁and R range from 3 to about 8. The disclosed reaction product may beemployed in the gelling of hydrocarbon liquids when used with a compoundcontaining a multivalent metal cation.

U.S. Pat. No. 5,271,464 to McCabe is directed to a method of plugging orsealing a subterranean formation by introducing a rapidly gellinghydrocarbon thereto. To the hydrocarbon is added a first component whichis an at least partially neutralized alkyl orthophosphate ester and asecond component which is the reaction product of an aqueous source ofaluminum or ferric ions and a C₈-C₁₈ surface active amine in thepresence of a water miscible organic solvent. The surface active amineis as defined above for European Pat. Application No. 551021A1, also toMcCabe. The water miscible organic solvent is generally a monohydricalcohol. U.S. Pat. No. 3,494,949 to Monroe et al. is directed to anadditive for improving the viscosity of motor oils which is generally analuminum salt of an alkyl orthophosphate.

U.S. Pat. No. 2,983,678 to Pellegrini et al. is directed to an additivefor lubricating oils which is generally a rare earth metal salt of adiester phosphate.

U.S. Pat. No. 6,004,908 and U.S. Pat. No. 6,147,034 are directed to anovel gel compositions for improved performance during fracturing.

In an article published at the Canadian International PetroleumConference Petroleum Society by Taylor, et. al. on Jun. 8-10, 2004entitled “Refinery Plugging by Residual Oil Gellant Chemicals in Crude:Understanding and Preventing the Problem through New Oil GellantChemistry” the role of tray plugging of the refinery distillation traysfrom the decomposition/volatile products of the phosphoric acid estergelling additive was clearly detailed. This plugging causes down time atthe refinery distillation facility leading to much higher costs andpoorer quality.

Distillation trays in the temperature range of 230 to 290° C. producedthe majority of volatile phosphorus compounds that condensed out of thegas phase and caused plugging of the holes in the trays.

Plugging of trays reduces the efficiency of distillation towers. Infact, if plugging becomes severe enough, it becomes necessary to shutdown the refinery to clean the towers. Unscheduled refinery shutdownscan be extremely costly to refiners. It is also possible that phosphorusmay still be present in some distillate streams such as the jet fueldraw.

U.S. Pat. Nos. 6,511,944 and 6,544,934 disclosed improved methods forfracturing subterranean formations using gelled liquid hydrocarbonswhich comprised the following steps: An improved gelled liquidhydrocarbon fracturing fluid is prepared comprised of a hydrocarbonliquid, a gelling agent comprised of a ferric iron or aluminumpolyvalent metal salt of a phosphonic acid ester, a proppant material,water and an amount of a delayed gel breaker effective to break thegelled hydrocarbon fracturing fluid. The phosphoric acid ester utilizedin the gelling agent which minimizes volatile phosphorus in refinerydistillation towers has the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsand R′ is an alkyl group having from about 1 to about 4 carbon atoms.After the gelled liquid hydrocarbon fracturing fluid is prepared, thesubterranean formation to be fractured is contacted with the gelledliquid hydrocarbon fracturing fluid under conditions effective to createat least one fracture in the subterranean formation.

U.S. Pat. No. 6,511,944 above disclosed that the phosphonic acid esterused in their invention must have an R equal to tetradecyl when R′ ismethyl to significantly reduce volatile emissions. This methyltetradecyl product is not commercially available and would be expectedto be expensive if made commercially available. While a variety ofsystems are available for gelling hydrocarbon liquids for theapplications discussed above, there exists a clear need in the art for ameans of improving the known phosphorous gelling agent systems toinclude those that are readily available and low cost, but also have lowvolatility are not subject to decomposition under oil drilling andrefinery conditions.

SUMMARY OF INVENTION

The present invention provides improved methods of using and preparinggelled liquid hydrocarbons, improved liquid hydrocarbon gelling agentsand improved gelled liquid hydrocarbon compositions which meet the abovedescribed needs and overcome the deficiencies of the prior art.

The improved methods of this invention for fracturing subterraneanformations using gelled liquid hydrocarbons are basically comprised ofthe following steps. An improved gelled liquid hydrocarbon fracturingfluid is prepared comprised of a hydrocarbon liquid, a gelling agentcomprised of a ferric iron or aluminum polyvalent metal salt of aphosphoric acid ester, a proppant material, water and an amount of adelayed gel breaker effective to break the gelled hydrocarbon fracturingfluid. The phosphoric acid ester utilized in the gelling agent whichminimizes volatile phosphorus in refinery distillation towers has theformula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is an alkyl group having from about 4 to8 carbon atoms. After the gelled liquid hydrocarbon fracturing fluid isprepared, the subterranean formation to be fractured is contacted withthe gelled liquid hydrocarbon fracturing fluid under conditionseffective to create at least one fracture in the subterranean formation.

It is, therefore, an object of the present invention to provide improvedmethods and compositions useful in treating subterranean formations aswell as in other similar applications.

It is a further objective of this work to reduce volatile phosphorousbased gelling agents and their decomposition products that are collectedduring distillation.

Other and further objects, features and advantages of the presentinvention will be readily apparent to those skilled in the art upon areading of the description of preferred embodiments which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical description of the products formed in the exampleof the novel phosphorous gelling agent that is the subject of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides methods of treating subterraneanformations penetrated by well bores with gelled liquid hydrocarbonfluids. The gelled liquid hydrocarbon fracturing fluids have heretoforebeen formed with a gelling agent comprised of a ferric iron or aluminumpolyvalent metal salt of a phosphoric acid ester. The current phosphoricacid esters use suffer from the problem that they decomposes in refinerydistillation towers to form volatile phosphorus which condenses on thetrays of the distillation towers and causes plugging. Also, thephosphoric acid ester may itself be volatile, dependent upon itsmolecular weight. By the present invention, improved methods andcompositions for fracturing subterranean formations with gelled liquidhydrocarbon fracturing fluids are provided wherein the gelling agentutilized is a ferric iron or aluminum polyvalent metal salt of aphosphoric acid ester with substituents that prevent volatilization anddegradation of the material.

Thus, the improved methods of fracturing subterranean formations of thepresent invention are basically comprised of the following steps. Agelled liquid hydrocarbon fracturing fluid is prepared comprised of ahydrocarbon liquid, a ferric iron or aluminum polyvalent metal salt of aphosphoric acid ester, a proppant material, water and an amount of adelayed gel breaker effective to break the gelled liquid hydrocarbonfracturing fluid. The phosphoric acid ester has the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is an alkyl group having from about 4 to8 carbon atoms. After the gelled liquid hydrocarbon fracturing fluid isprepared, the subterranean formation to be fractured is contacted withthe fracturing fluid under conditions effective to create at least onefracture in the subterranean formation.

The hydrocarbon liquid utilized to form the gelled liquid hydrocarbonfracturing fluid can be any of the various previously used hydrocarbonliquids including, but not limited to, olefins, kerosene, diesel oil,gas oil (also known as gas condensate), fuel oil, other petroleumdistillates, and certain mixtures of crude oil. Liquid hydrocarbonfracturing fluids which are specifically designed for use with CO2 aregenerally preferred. Such a liquid hydrocarbon fracturing fluid iscommercially available from the Trysol Corporation of Sundre, Alberta,Canada under the trade name “FRACSOL™”

The gelling agent utilized for gelling the hydrocarbon liquid whereby ithas a high viscosity sufficient to carry suspended proppant material andproduce fractures in a subterranean formation is a ferric iron oraluminum polyvalent metal salt of a phosphoric acid ester having theformula set forth above. The polyvalent metal salt of the phosphoricacid ester is preferably produced at the well site by adding thephosphoric acid ester, and preferably, at least a stoichiometric amountof a polyvalent metal salt (preferably a ferric iron salt or an aluminumcompound). In addition, if water is not already contained in thehydrocarbon liquid or added thereto as a component in a cross-linkersolution or the like, water is added to the hydrocarbon liquid in anamount, for example, of about 0.05% or greater by weight of thehydrocarbon liquid. The presence of the water allows slowly watersoluble or encapsulated breakers to be dissolved or released. See, forexample, Smith et al. U.S. Pat. No. 5,846,915 issued on Dec. 8, 1995which is incorporated herein by reference.

When a ferric iron salt is utilized to form the gelling agent, it ispreferably selected from ferric sulfate or ferric chloride with ferricsulfate being preferred. The ferric iron salt is typically mixed withamines, surfactants and water to form a liquid cross-linking solution.An example of a commercially available ferric iron cross-linkingsolution is “EA-3™” cross-linking solution sold by Ethox Chemicals, Inc.of Greenville, S.C. When an aluminum compound is utilized, it ispreferably selected from aluminum chloride or aluminum isopropoxide,with aluminum chloride being the most preferred. The polyvalent metalcompound utilized reacts with the phosphoric acid ester to form thehydrocarbon liquid gelling agent of this invention which gels thehydrocarbon liquid. The phosphoric acid ester is added to thehydrocarbon liquid along with the polyvalent metal source to form thegelling agent in the hydrocarbon liquid in an amount in the range offrom about 0.1% to about 2.5% by weight of the hydrocarbon liquid.

As mentioned above, the phosphoric acid ester which can be utilized toform the hydrocarbon liquid gelling agent of this invention has theformula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is an alkyl group having from about 4 to8 carbon atoms. Techniques which can be utilized for the preparation ofthe phosphoric acid esters useful in accordance with this invention are,for example, described in U.S. Pat. No. 3,798,162 issued to Dickert, Jr.on Mar. 19, 1974 which is incorporated herein by reference.

Proppant materials which can be utilized in the fracturing fluids ofthis invention are well known in the art. For example, proppantmaterials such as graded sand, resin coated sand, sintered bauxite,various particulate ceramic materials, glass beads and the like can beutilized. The particular size of the proppant material employed dependson the particular formation being fractured and other variables.Generally, the proppant particle sizes are in the range of from about 2to about 200 mesh on the U.S. Sieve Series scale.

A variety of delayed gel breakers can be utilized in accordance with thepresent invention to cause the gelled liquid hydrocarbon fracturingfluid to revert to a thin fluid that is produced back after fracturesare formed in a subterranean formation. The gel breakers can bematerials which are slowly soluble in water which, as mentioned above,is combined with or otherwise present in the hydrocarbon liquid. Thebreaking of the gel does not take place until the slowly solublebreakers are dissolved in the water.

One example of a delayed gel breaker is a hard burned magnesium oxide.Others include alkali metal carbonates, bicarbonates and acetates. Alsoincluded in this group are alkaline earth oxides and hydroxides, weakacids and reducing agents (with metal crosslinkers such as iron). Thesegel breakers can be used with encapsulating materials.

The gel breaker utilized in a water-containing gelled liquid hydrocarbonfracturing fluid of this invention is generally present therein in anamount in the range of from about 0.01% to about 3% by weight of thehydrocarbon liquid, more preferably in an amount in the range of fromabout 0.05% to about 1%.

A preferred method of fracturing a subterranean formation in accordancewith the present invention is comprised of the steps of: (a) preparing agelled liquid hydrocarbon fracturing fluid comprised of a hydrocarbonliquid, a ferric iron or aluminum polyvalent metal salt of a phosphoricacid ester, the phosphoric acid ester having the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is a butyl group. A proppant material,water and an amount of a delayed gel breaker effective to break thegelled hydrocarbon fracturing fluid; and (b) contacting the subterraneanformation with the gelled hydrocarbon fracturing fluid under conditionseffective to create at least one fracture in the subterranean formation.

The ferric iron or aluminum polyvalent metal salt of the phosphoric acidester is present in the fracturing fluid in an amount in the range offrom about 0.1% to about 2.5% by weight of the hydrocarbon liquid in thefracturing fluid, more preferably in an amount in the range of fromabout 0.2% to about 1%. The proppant material is present in thefracturing fluid in an amount in the range of from about 1 to about 14pounds of proppant material per gallon of hydrocarbon liquid in thefracturing fluid. As mentioned, water is added to or otherwise containedin the hydrocarbon liquid so that the delayed gel breaker utilized isdissolved in the water. The delayed gel breaker is present in thefracturing fluid in an amount in the range of from about 0.01% to about3% by weight of the hydrocarbon liquid in the fracturing fluid, morepreferably in an amount in the range of from about 0.05% to about 1%.

A preferred method of preparing a gelled liquid hydrocarbon fluid ofthis invention is comprised of adding a phosphoric acid ester to ahydrocarbon liquid, the phosphoric acid ester having the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is an alkyl group having from about 4 to8 carbon atoms, at least a stoichiometric amount of a polyvalent metalsource selected from ferric iron salts and aluminum compounds whichreacts with the phosphoric acid ester to form a ferric iron or aluminumpolyvalent metal salt thereof, water and an amount of a delayed gelbreaker effective to break the gelled hydrocarbon fracturing fluid.

The ferric iron or aluminum polyvalent metal salt of the phosphoric acidester formed in the hydrocarbon liquid is present therein in an amountin the range of from about 0.1% to about 2.5% by weight of thehydrocarbon liquid, more preferably in an amount in the range of fromabout 0.2% to about 1%. The delayed gel breaker utilized is present inthe hydrocarbon liquid in an amount in the range of from about 0.01% toabout 3% by weight of the hydrocarbon liquid, more preferably in anamount in the range of from about 0.05% to about 1%.

A preferred hydrocarbon liquid gelling agent of this invention iscomprised of a ferric iron or aluminum polyvalent metal salt of aphosphoric acid ester, the phosphoric acid ester having the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is an alkyl group having from about 4 to8 carbon atoms.

A more preferred hydrocarbon liquid gelling agent is comprised of aferric iron polyvalent metal salt of a phosphoric acid ester, the esterhaving the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is a butyl group. A preferred gelledliquid hydrocarbon composition of this invention is comprised of: ahydrocarbon liquid; a gelling agent comprising a polyvalent metal saltof a phosphoric acid ester produced from a phosphoric acid ester and aferric iron salt or an aluminum compound, the phosphoric acid esterhaving the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is a methyl group, water and a delayedgel breaker present in an amount effective to break the gel formed bythe gelling agent and the hydrocarbon liquid.

As mentioned above, the delayed gel breaker can be alkaline earth metaloxides including hard burned magnesium oxide, alkali metal carbonates,alkali metal bicarbonates, alkali metal acetates, alkali metalhydroxides, amines and weak acids which are slowly water soluble or areencapsulated with a slowly water soluble or other similar encapsulatingmaterial. The delayed gel breaker can also be a reducing agent thatreduces ferric iron to ferrous iron encapsulated with a slowly watersoluble or other similar encapsulating material. The delayed gel breakeris present in the gelled hydrocarbon liquid in an amount in the range offrom about 0.01% to about 3% by weight of the hydrocarbon liquid, morepreferably in an amount in the range of from about 0.05% to about 1%.

As will be understood by those skilled in the art, the use of theimproved liquid hydrocarbon gelling agents and gelled liquid hydrocarboncompositions is not limited to fracturing subterranean formations. Forexample, the gelled liquid hydrocarbon compositions can be used forforming gravel packs in well bores, in pipeline pigging operations andin other operations where a gelled hydrocarbon liquid which subsequentlybreaks into a thin fluid is utilized.

In order to further illustrate the methods and composition of thepresent invention, the following examples are given.

EXAMPLES

A number of phosphoric acid esters have been synthesized according toU.S. Pat. Nos. 6,342,468 and 5,110,485 the entire contents of which areincorporated by reference.

The following laboratory procedure was used in the preparation of theabove esters according to U.S. Pat. Nos. 6,342,468 and 5,110,485.

The procedure for making the phosphate esters using the reactants inTable 1 is as follows:

A 4-neck reaction flask was used, equipped with a thermometer,mechanical stirrer, condenser and gas (N₂) inlet. 39.37 grams oftributyl phosphate and 14.96 grams of phosphorous pentoxide were addedto the flask, mixed and reacted for two hours at 175° F. to produce apolyphosphate intermediate. All additions and reactions throughout theexperiment were conducted under a nitrogen blanket. The polyphosphateintermediate was cooled to approximately 140° F. A mixture of 7.31 gramsof Dowanol EPH and 38.36 grams of Epal 810 was then added dropwise tothe polyphosphate intermediate while maintaining a temperature betweenabout 140°-175° F. After the alcohol blend addition, the mixture washeated at 250°-260° F. for two hours. The reaction resulted in a liquidalkyl phosphate diester.

TABLE 1 Reaction Formulation Reactant % Tributyl Phosphate 39.37 P2O514.96 Dowanol EPH 7.31 Epal 810 38.36

Where Dowanol EPH is a phenyl ether comprised of a one mole adduct ofphenol.

And Epal 810 is a commercial blend of Octanol and Decanol.

The reaction products are listed in FIG. 1. These include two alkylproducts and one phenyl alkyl ether product.

Low Phosphorous Analysis was conducted using the “Standard Method forDistillation of Petroleum Products at Atmospheric Pressure” Designation:D86-04b. Distillate was analyzed for Phosphorous by a contractlaboratory using an ICP Analyzer (Inductively Coupled Plasma)

The distillation setup was as follows:

Gel sampled is comprised of a phosphate gelling agent, activator, #2Diesel, and gel breaker. Sample is placed in bath for 24 hours to allowbreaker to decay gel formed. 150 mls. of broken gel sample was placed inthe distillation flask and heat was applied as prescribed by the method.

Distillation was repeated five times on each gel system and samplescollected submitted for Phosphorous Analysis. Results are in Table 2.

TABLE 2 Distillation Phosphorous Results Mixture I.D. Sample I.D. mLs ofDistillate Phos. ppm Mixture A EG-2/EA-3 BK18-018 A 55 79 BK18-018 B 6047 BK18-018 C 62 71 BK18-018 D 64 70 BK18-018 E 63 70 Mixture BEG-2B/EA-3 BK18-019 A 65 32 BK18-019 B 64 12 BK18-019 C 67 12 BK18-019 D72 21 BK18-019 E 69 16 Mixture C EG-2B10K/EA-3 BK18-020 A 72 11 BK18-020B 74 9.5 BK18-020 C 72 18 BK18-020 D 74 9.5 BK18-020 E 75 9.9 Mixture DEG-2B10K/4071 BK18-021 A 75 49 BK18-021 B 73 20 BK18-021 C 72 19BK18-021 D 73 9.5 BK18-021 E 74 13 Mixture E EG-2B10K/4111 BK18-022 A 799.8 BK18-022 B 78 9.8 BK18-022 C 76 9.7 BK18-022 D 76 12 BK18-022 E 778.9 ICP Phosphorous Detection Limit is approximately 10 ppm.

Sample Description

Mixture A—EG-2/EA-3—Standard commercial productMixture B—EG-2B/EA-3—New Molecule+commercial activatorMixture C—EG-2B10K/EA-3—New Molecule partially KOHneutralized+commercial activatorMixture D—EG-2B10K/4071—New Molecule partially KOH neutralized+alternatecommercial activatorMixture E—EG-2B10K/4111—New Molecule partially KOH neutralized+alternatecommercial activator

It can be seen that the standard commercial product used in Mixture Ahad phosphorous levels in the distillate that were between 47-79 ppm.The new phosphoric acid ester of this invention used in Mixture B hadphosphorous levels in the distillate between 12-32 ppm, a substantialreduction. When the new phosphoric acid ester of this invention waspartially KOH neutralized as in Mixture C, the phosphorous levels in thedistillate that were between 9.5-18 ppm. Some variation was seendepending on the nature of the activator in Mixtures D and E.

The entire contents including the references cited therein of all thecited patents and documents in this specification are incorporated byreference in their entirety for all purposes to the same extent as ifeach individual patent, patent application or publication were soindividually denoted.

While the many forms of the invention herein disclosed constitutepresently preferred embodiments, many others are possible and furtherdetails of the preferred embodiments and other possible embodiments arenot to be construed as limitations. It is understood that the terms usedherein are merely descriptive rather than limiting and that variouschanges many equivalents may be made without departing from the spiritor scope of the claimed invention.

1. A method of fracturing a subterranean formation comprising the stepsof: (a) preparing a gelled liquid hydrocarbon fracturing fluidcomprising a hydrocarbon liquid, a ferric iron or aluminum polyvalentmetal salt of a phosphoric acid ester, said phosphoric acid ester havingthe formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is an alkyl group having from about 4 to8 carbon atoms a proppant material, water and an amount of a delayed gelbreaker effective to break said gelled hydrocarbon fracturing fluid; and(b) contacting said subterranean formation with said gelled hydrocarbonfracturing fluid under conditions effective to create at least onefracture in said subterranean formation.
 2. The method of claim 1wherein said hydrocarbon liquid is selected from the group consisting ofolefins, kerosene, diesel oil, gas oil, fuel oil, petroleum distillateand crude oil.
 3. The method of claim 1 wherein said polyvalent metalsalt of a phosphoric acid ester is produced by reacting said phosphoricacid ester with a ferric iron compound.
 4. The method of claim 1 whereinsaid polyvalent metal salt of a phosphoric acid ester is produced byreacting said phosphoric acid ester with an aluminum compound.
 5. Themethod of claim 1 wherein said ferric iron or aluminum polyvalent metalsalt of a phosphoric acid ester is present in said hydrocarbon liquid inan amount in the range of from about 0.1% to about 2.5% by weight ofsaid hydrocarbon liquid.
 6. The method of claim 1 wherein said delayedgel breaker is selected from the group consisting of magnesium oxide,alkali metal carbonates, alkali metal bicarbonates, alkali metalacetates, alkali metal hydroxides, amines and weak acids which areslowly water soluble or are encapsulated with a slowly water solubleencapsulating material.
 7. The method of claim 1 wherein said delayedgel breaker is slowly water soluble hard burned magnesium oxide.
 8. Themethod of claim 3 wherein said delayed gel breaker is a reducing agentthat reduces ferric iron to ferrous iron.
 9. The method of claim 1wherein said gel breaker is present in said gelled hydrocarbon liquid inan amount in the range of from about 0.01% to about 3% by weight of saidhydrocarbon liquid.
 10. A method of preparing a gelled liquidhydrocarbon fracturing fluid comprising adding a phosphoric acid esterto a hydrocarbon liquid, the phosphoric acid ester having the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is an alkyl group having from about 4 to8 carbon atoms, at least a stoichiometric amount of a polyvalent metalsource selected from ferric iron salts and aluminum compounds whichreacts with said phosphoric acid ester to form a ferric iron or aluminumpolyvalent metal salt thereof, water and an amount of a delayed gelbreaker effective to break said gelled hydrocarbon fracturing fluid. 11.The method of claim 10 wherein said hydrocarbon liquid is selected fromthe group consisting of olefins, kerosene, diesel oil, gas oil, fueloil, petroleum distillate, and crude oil.
 12. The method of claim 10wherein said ferric iron or aluminum polyvalent metal salt of saidphosphoric acid ester formed in said hydrocarbon liquid is presenttherein in an amount in the range of from about 0.1% to about 2.5% byweight of said hydrocarbon liquid.
 13. The method of claim 10 whereinsaid delayed gel breaker is selected from the group consisting ofmagnesium oxide, alkali metal carbonates, alkali metal bicarbonates,alkali metal acetates, alkali metal hydroxides, amines and weak acidswhich are slowly water soluble or are encapsulated with a slowly watersoluble encapsulating material.
 14. The method of claim 10 wherein saiddelayed gel breaker is slowly water soluble hard burned magnesium oxide.15. The method of claim 10 wherein said delayed gel breaker is areducing agent that reduces ferric iron to ferrous iron.
 16. The methodof claim 10 wherein said gel breaker is present in said gelledhydrocarbon liquid in an amount in the range of from about 0.01% toabout 3% by weight of said hydrocarbon liquid.
 17. A gelled liquidhydrocarbon fluid composition comprising: (a) a hydrocarbon liquid; (b)a gelling agent comprising a polyvalent metal salt of a phosphoric acidester produced from a phosphoric acid ester and a ferric iron salt or analuminum compound, said phosphoric acid ester having the formula

wherein R is an alkyl group having from about 8 to about 24 carbon atomsor R is a phenyl alkyl ether having from about 2 to 12 alkyl carbonatoms and 1 phenyl group and R′ is an alkyl group having from about 4 to8 carbon atoms, (c) water; and (d) a delayed gel breaker present in anamount effective to break the gel formed by said gelling agent and saidhydrocarbon liquid.
 18. The composition of claim 17 wherein R is analkyl group having from 8 to 10 carbon atoms.
 19. The composition ofclaim 17 wherein R′ is an alkyl group having from 4 to 5 carbon atoms.20. The composition of claim 17 wherein R′ is butyl.
 21. The compositionof claim 17 wherein said hydrocarbon liquid is selected from the groupconsisting of olefins, kerosene, diesel oil, gas oil, fuel oil,petroleum distillate, and crude oil.
 22. The composition of claim 17wherein said ferric iron salt is selected from the group consisting offerric sulfate and ferric chloride.
 23. The composition of claim 17wherein said aluminum compound is selected from the group consisting ofaluminum chloride, aluminum sulfate and aluminum isopropoxide.
 24. Thecomposition of claim 17 wherein said ferric iron or aluminum polyvalentmetal salt of said phosphoric acid ester is present in said hydrocarbonliquid in an amount in the range of from about 0.1% to about 2.5% byweight of said hydrocarbon liquid.
 25. The composition of claim 17wherein said delayed gel breaker is selected from the group consistingof magnesium oxide, alkali metal carbonates, alkali metal bicarbonates,alkali metal acetates, alkali metal hydroxides, amines and weak acidswhich are slowly water soluble or are encapsulated with a slowly watersoluble encapsulating material.
 26. The composition of claim 17 whereinsaid delayed gel breaker is slowly water soluble, hard burned magnesiumoxide.
 27. The composition of claim 17 wherein said delayed gel breakeris a reducing agent that reduces ferric iron to ferrous ironencapsulated with a slowly water soluble encapsulating material.
 28. Thecomposition of claim 27 wherein said gel breaker is present in saidgelled hydrocarbon liquid in an amount in the range of from about 0.01%to about 3% by weight of said hydrocarbon liquid.
 29. (canceled)